20 replies to this topic

[johnnysti]

Hi all

Ive just done a compression check on my car as it is running very badly and found the following


Cyl. 1 150
Cyl. 2 175
Cyl. 3 175
Cyl. 4 150


Can anyone point out what the problem may be? Ive had the head wrked by slark to match their SR2 http://www.slarkrace...co.uk/heads.htm

Ive replaced the spark plugs at a cost of £38, fitted a brad new weber at £300, fitted a set of full roller tips from minispeed at £200 but it hast run properly since the head work. But with all that said, i dont think its the valves or anything internal with the head anyway.

Please can someone help as its not been the same since June!!!

Johnny

[The Matt]

What is the car actually doing? Lumpy idle? Misfires through the rev range? Lack of power?

I certainly think it is something that you should talk to Slark about. Generally, perfomance engines won't run as smoothly as standard ones (depending on other things like cam choice etc), but there does seem to be an imbalance with the compression on the outer cylinders from the results you have posted.

I don't know if there would be any reason to have a different compression ratio etc. on the outer cylinders, perhaps it is down to some quirk of the siamese port layout of the engines? Again, Slark are the experts and they are the ones that have sold you the head.

[Retro_10s]

also... i hope you've rolling roaded this car!

could the weber cause problems>?

[johnnysti]

I took it to the rolling road not so long ago, just after the head was fitted. They struggled to get any more power out of the car.

After fitting the full rockers, the cars running to a nose dive so i got a mobile tuning guy out who told me that there was no 'bang' from No.1 cyl.
I then took the car to my wifes uncle who has a garage and found that there was a problem with the weber and that the fuel was ignighting in the manifold. So off cam the weber and was sent to a specialist who told me it was mullered. Something about a shaft being worn like he had never seen before that also caused it to over fuel.
And thats where i am now. I dont want to RR it untill the compression is sorted. Will a RR session sort out the compression? I dont want to make things worse. Since fitting the head, the car has only done a few hundred miles at the very most.


Now when i drive it, it wants to bunny hop down the road untill i give it a bit more throttle and then it goes but doesnt give the car any power.

[The Matt]

The cars running took a nose dive after the rockers were fitted?

What valve clearances have you set the rockers to?

What camshaft are you running?

Did you change the rockers without changing the head gasket? If so, was it done with the engine cold?

There is also a possibilty that the overfuelling has casued a problem too.

[Retro_10s]

wierd.... sounds like dodgy fuelling with the bunny hop thing, but could it cause the compression issues?.. hmmm probaby not.


Ring slark.

[johnnysti]

The cars running took a nose dive after the rockers were fitted?

What valve clearances have you set the rockers to?

What camshaft are you running?

Did you change the rockers without changing the head gasket? If so, was it done with the engine cold?

There is also a possibilty that the overfuelling has casued a problem too.

Hi
We have worked out that it is a very mild 'town' cam, may even be standard. Thats why ive fitted the 1:5 tips. The rockers were fitted when the engine was cold but have been on and off three times, because after fitting them, we found that the rockers were not sitting properly as i wasnt told id need tower spacers due to the head skimming. In the end i got 3mm spacers. The gasket has not been changed. The clearences were set off the sizes given in one of the mini mag features a few months back on head work.

[Jammy]

What advice has Slark given you?

[Retro_10s]

The gasket has not been changed

tell me you don't mean the head gasket please!

[Bungle]

i had to replace the head gasket after fitting my roller rockers

some times you can get away with it but not very often :'(

[theoldtartspimp]

the reason might be that you have a gap in the head gasket between 2 & 3 this might explain why you compression is embalanced and higher on the 2 centre pistons (might not be but seeing they both come up at the same time might add compression)

when i put my rockers on i had to change the head gasket but think of it as a excuse to get a copper 1

i had my head gasket go between the bores (2 & 3) and it felt like it was running on three cylinders and sounded like a mini when the dizzy has got very wet misfiring and allsorts

Edited by theoldtartspimp, 17 October 2006 - 12:01 PM.

[The Matt]

Yep, that's what I was worried about. The rockers have been on and off and the head gasket has not been changed, therefore it is 'likely' that the head gasket is one of the problems.

Another possible problem I was thinking about is whether the valve clearances have allowed for increased valve lift (higher ratio rockers and different camshaft).

When you did the compression check, did you have all of the spark plugs out, or just one at a time?

[johnnysti]

Just spoke to the father-in-law and he did the compression check with all the spark plugs out.


Ive just driven it back from his and its driving better, still not right al all but the bunny hopping has gone. Just very lumpy.

[johnnysti]

Also, is there a different type of head gasket to use or is a standard one ok? its a 1293

Johnny

[theoldtartspimp]

i have a 1293 i'm just using a copper head gasket works a treat bit more expensive but safes changing it as often